The present invention relates generally to the field of golf club shafts. In particular, the present invention involves the use of metal coated fibers in forming composite golf club shafts to provide controllable feel and balance.
Frequently a golfer""s goal is to send the golf ball a greater distance, or, when fatigue or age are factors, to maintain a certain hitting distance. Although traditional golf club shafts are made from steel, there is a need for golf clubs which are lighter and specialized alternatives to steel in order to achieve these goals. Graphite shafts have reduced weight, greater flex and strength than steel, providing benefits such as vibration dampening on mis-hits, greater distance and reduced physical stress on the wrist, shoulder and elbow. Accordingly, graphite shafts are gaining in acceptance. Traditionally however, graphite shafts have suffered from inconsistent manufacturing, higher costs, extra torque, a soft feel and higher breakage rates, particularly around the club head connection or hosel.
Graphite golf clubs have been made from many different materials and recently have become available in different combinations of composites using fiber reinforced plastics and metals. Composite graphite shafts have normally been made by either a sheet-rolling method or a filament winding method.
In the sheet-rolling or sheet-wrapping method, carbon, glass or other fibers are impregnated with a plastic resin and placed in a parallel matrix to form a broad sheet or prepreg. The prepreg is then cut into smaller sheets similar to a tapered flag shape with all of the fibers at a particular angle to the axis of the intended mandrel, the angle can be between 0xc2x0 and 90xc2x0. These flags are then rolled around a mandrel to form various layers or plies. The layers are then cured to form a composite and the mandrel is removed.
In the filament winding method, fibers are collected into groups called xe2x80x9ctowsxe2x80x9d and each tow is impregnated with resin and wrapped around the mandrel to form the layers prior to curing. Filament winding generally results in an improved shaft with greater consistency in manufacture. The resulting shafts are substantially lighter than traditional metal shafts.
Preferably a golf club including the shaft and head should be xe2x80x9ctunedxe2x80x9d or customized to a particular player or overall club design in terms of weight, balance, torque, impact strength and flex. Composite shafts have been criticized, among other reasons, as difficult to tune for particular players. For example, sheet-wrapped shafts have been criticized as providing too much torque to the ball, while filament wound shafts have been criticized as having greater breakage rates.
Moreover, a shaft""s weight, balance, impact strength and flex are interdependent so that attempting to adjust one characteristic frequently has undesired effects on other attributes. For example, including a sufficient number of carbon-fiber layers to achieve a desired weight can make the shaft too thick, effecting its stiffness and balance. It would be desirable to customize particular attributes of a shaft while maintaining the desirable characteristics of graphite composites and not negatively impacting other attributes of play.
As some attempts to solve these problems, metals have been used in conjunction with composite shafts, but the combinations of materials and composites have not had the desired results. Use of metal reinforcement to date has consisted of using extruded tubing, amorphous metal tape wound as one or more layers of the shaft, or plating added to the outer layer of the shaft. These hybrid shafts, using combinations of fiber-reinforced plastics and metals, have yet to achieve widespread use due to higher material and production costs without significant performance improvement. While achieving one favorable effect, the weight, placement or design of the metals often effects other attributes undesirably.
One example of such an attempt is illustrated in U.S. Pat. No. 5,601,892 issued to McIntosh. McIntosh suggests sheet-rolled hollow rods formed with non-coated sheet-rolled inner plies covered by one or two plies of sheet-rolled nickel-coated flags. McIntosh suggests that the fibers in the outer plies be oriented substantially parallel to the rod axis. McIntosh states that this will increase impact strength. McIntosh fails to address the concerns of weight, balance and torque. Although McIntosh mentions to golf clubs, McIntosh focuses on fishing rods and does not address many of the specific concerns encountered in manufacturing golf club shafts. Thus there remains a need for improved golf club shafts.
The prior art does not allow for the easy placement of weight or altered weight designs within the golf shaft without significantly affecting other shaft performance attributes. While sometimes desirable, this is most often not the case.
A golf club shaft is formed with an elongated body using a combination of fiber-reinforced plastics and metal-coated fibers to assist in obtaining an optimally characterized golf club for a particular player. Preferably a sheet-rolled or filament wound core is covered by a filament wound outer layer having at least one ply including metal-coated fibers. The fibers can be coated with various metals such as nickel, titanium, platinum, zinc, copper, brass, tungsten, cobalt, gold or silver.
The use of metal-coated fibers allows the use of combinations of fiber reinforced plastic and metal-coated fibers in plies for producing golf shafts with optimum performance properties. For example, the use of metal-coated fibers allows the addition of weight to the shaft without significantly influencing its longitudinal or torsional rigidity. There has been a widespread, unsolved demand for this type of product. Metal-coated fibers can be used to enhance the feel and sensitivity of the golf club shaft to suit the needs of a particular design or player.
In alternate embodiments, specific placement of the metal-coated carbon fibers is possible through filament winding to add weight to predetermined points in the shaft to shift the flex and balance points without varying the shaft""s torsional properties and while still providing the optimum flex for a given golf club design. In still further embodiments, fibers coated with different metals can be used to form different portions of the shaft.
It is an object of the invention to provide an improved golf club shaft.
It is another object of the invention to provide a golf club shaft which includes metal-coated fibers.
It is a further object of a preferred embodiment of the present invention to provide a composite graphite golf shaft used in forming a golf club which may be tuned for a particular player or overall club design.
Further objects, features and advantages of the present invention shall become apparent from the detailed drawings and descriptions provided herein.